The present invention relates to a brushless motor which can be used, for example, as an electric motor provided with a reduction mechanism for feeding paper money that has been inserted into a vending machine into a paper money transport path.
For example, Japanese Utility Model Registration Publication No. 2532489 describes a brushless motor covered by a frame (cover member). In this brushless motor an armature core (stator core) is fastened to the outside of an insulator (bearing holder), which is fastened to a printed circuit board (retaining plate), and a magnet (rotor magnet) that faces the outside of this armature core is fastened to the inner circumferential face of a rotor frame (rotor case). A rotary shaft that is fastened to the center of this rotor frame is supported by an oil-impregnated sintered bearing that is fastened to the center of the frame, and by an oil-impregnated sintered bearing that is fastened to the printed circuit board, and the top end of the rotary shaft protrudes from the frame.
However, with a structure such as described above, the rotary shaft is supported by an oil impregnated sintered bearing fastened to the center of the frame, and by an oil impregnated sintered bearing fastened to the printed circuit board, and thus these bearings can easily become misaligned. If these two bearings become misaligned, there are problems insomuch as, for example, abnormal wear of the bearings and the rotary shaft and twisting tend to occur, resulting in noise, and reducing the durability of the brushless motor.
While it is possible to limit misalignment between the two bearings by increasing the precision with which the frame and the printed circuit board are assembled, this will increase manufacturing costs.
Here, the problem of bearing misalignment can be eliminated, for example, by adopting a configuration in which the rotary shaft is supported by only one of the bearings. However, in the particular case in which the brushless motor is used as an electric motor provided with a reduction mechanism, there is a risk that the rotary shaft will be deformed if an excessive load from the radial direction is applied to the rotary shaft that protrudes from the frame (cover member).